CAMBRIDGE, Mass. — Smart wristbands have become increasingly popular tools among people interested in tracking data about themselves, from their heart rate to their movement during daily activities. In the future, these devices could also help people understand the symptoms of conditions such as autism and depression, researchers say.

In a series of studies over the past decade, researchers at the Massachusetts Institute of Technology have analyzed data from wristbands to see how people's heart rate, temperature, movement and skin conductance correlate with symptoms of an array of physical and developmental conditions.

These researchers have recently focused their work on children with autism, and have found that these children's expression of their emotions often does not correlate with their internal arousal state as indicated by wristband data. For instance, a child with autism might appear to be experiencing a high-energy episode when, in fact, wristband data indicates that their internal state is calm.

"[Teachers] will see someone jumping up and down, and say, 'Maybe someone should calm that kid down,' but we read out his internal state, and see his state is so low that this kid needs 20 minutes on a trampoline before he gets to a normal level," Rosalind Picard, director of the Affective Computing Research Group at MIT, said during a lecture here at Harvard University on March 12.

Picard said she considers the whole suite of body data during her analyses, but uses skin conductance as the main way to determine a child's internal state. Skin conductance is the ability of skin to conduct an electrical current, and increases with moisture, for example, when someone sweats.

Skin conductance generally increases when the body's fight-or-flight response is triggered, and also during periods of positive excitement. Even when a person does not feel particularly sweaty, changes in their emotional state can cause small changes in their sweat glands that raise their skin conductance. [Best Fitness Trackers — 2014]

Pairing skin conductance data with written logs about a child's behavior throughout a given day could help researchers determine which types of activities and therapy work well for a child, and which are disruptive to the child, Picard said. This could be particularly helpful for people unable to describe their emotions in words, which is the case for some people with autism, Picard said.

Beyond their autism research, Picard's team also recently launched a long-term study to assess how skin-conductance data may help people with depression understand what triggers bouts of stress and anxiety. Therapists who treat people with depression often use questionnaires to understand their patients' triggers, but these questionnaires can be subjective. Wristband data, on the other hand, can help pinpoint the moments when stress levels become elevated throughout the day, such as the arrival of a spouse home from work, or an interaction with a friend.

"That's the stuff the questionnaires just don't [tell] you," Picard told Live Science. "We think we are going to get complementary information. We don't know yet what we are going to get, but we will mine the data and see."

People without mental health conditions may also find that wristbands are useful during difficult times, such as short bouts of depression or sleep problems.

"Everybody goes through highs and lows and good times and bad," Picard said. Some may want a tool to help them understand those times.

However, wristbands alone will not provide the information required to improve therapy, because both positive and negative emotions can increase skin conductance. Rather, contextual information about a person's day will always be necessary to make use of the wristband data.

"Skin conductance without context is pretty meaningless," Elliot Hedman, a graduate student in Picard's lab, told Live Science. "The context is what helps make it so we can interpret the data."

The results generated by the devices will differ among people, because conditions such as autism and depression vary widely across people. But as more and more people use the devices and more data is compiled, broader discoveries about these conditions and how they can be treated may arise, Hedman said.